Aidan;

I did a lot of research in the mid '80s, before commiting to DOT 5 for all of my hydraulic systems, including reviewing an engineering data sheet from GE when they were the big producer (I don't know if this is still the case). Then we did Girling seal compatibility tests for 6 months, including combined with exposure to UV. This showed good seal compatibility, and no softening or attack.

Only after everything looked positive, did our circle of 122 and 1800 driving aquaintances start using it on hydraulic clutch cylinders (Bob G. went from YEARLY clutch hydraulics rebuildings with DOT4 to over 10 years(!!!!!) on the J5Rocket No.3 - this is no exaggeration), and only after the rebuild intervals on those went up significantly did we start using it in brake systems. Result: Perfectly satisfatory performance, and significantly higher service intervals there too...and I don't think I EVER got it hot enough to experience the soft pedal due to hot compressibility, just the racers did, but I DID experience soft pedals presumably from either air in the system - like in that rear brake valve/pressure reducer - or micro-aeration, or some combination thereof, in any case, a second or third bleeding always cured that. Currently, I'm still using (and recommending) it.

I've yet to disassemble a rear brake valve/pressure-reducer to inspect its guts...I just push a reservoir's worth of fluid through each rear corner when bleeding and so figure it's adequitely flushed (maybe presumptionsly). Often, multiple bleedings are necessary because the rear brake valve often traps air. My inspection of the official factory green manuals shows that there are some seals within this device.

I've done a fair amount of searching and surfing and tried to compile what I consider to be the best information including their URL sources. I just recently added a bunch of info and links. See: http://www.intelab.com/swem/Amazoning%20with%20Silicon%20Brake%20Fluid.htm

Cheers